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Top 10 dos mais citados do International Journal of Multiphase Flow:

Rodriguez, O.M.H. and Oliemans, R.V.A., Experimental study on oil-water flow in horizontal and slightly inclined pipes, International Journal of Multiphase Flow, Volume 32, Issue 3, 2006, Pp 323-343

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Artigo em Destaque

Top 10 Cited (articles published in the last five years) Extracted from Scopus (on Fri Jun 11 20:22:01 BST 2010)

Experimental study on oil-water flow in horizontal and slightly inclined pipes

Rodriguez, O.M.H.^a b , Oliemans, R.V.A.^a  

Oil-water two-phase flow experiments were conducted in a 15 m long, 8.28 cm diameter, inclinable steel pipe using mineral oil (density of 830 kg/m ³ and viscosity of 7.5 mPa s) and brine (density of 1060 kg/m ³ and viscosity of 0.8 mPa s). Steady-state data on flow patterns, two-phase pressure gradient and holdup were obtained over the entire range of flow rates for pipe inclinations of -5°, -2°, -1.5°, 0°, 1°, 2° and 5°. The characterization of flow patterns and identification of their boundaries was achieved via observation of recorded movies and by analysis of the relative deviation from the homogeneous behavior. A stratified wavy flow pattern with no mixing at the interface was identified in downward and upward flow. Two gamma-ray densitometers allowed for accurate measurement of the absolute in situ volumetric fraction (holdup) of each phase for all flow patterns. Extensive results of holdup and two-phase pressure gradient as a function of the superficial velocities, flow pattern and inclinations are reported. The new experimental data are compared with results of a flow pattern dependent prediction model, which uses the area-averaged steady-state two-fluid model for stratified flow and the homogeneous model for dispersed flow. Prediction accuracies for oil/water holdups and pressure gradients are presented as function of pipe inclination for all flow patterns observed. There is scope for improvement for in particular dual-continuous flow patterns.

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Experimental Thermal and Fluid Science

Volume 34, Issue 4, May 2010, Pages 463-473

Film thickness measurement techniques applied to micro-scale two-phase flow systems

Cristiano Bigonha Tibiriçáa, Francisco Júlio do Nascimentoa,  and Gherhardt Ribatski

Recently semi-empirical models to estimate flow boiling heat transfer coefficient, saturated CHF and pressure drop in micro-scale channels have been proposed. Most of the models were developed based on elongated bubbles and annular flows in the view of the fact that these flow patterns are predominant in smaller channels. In these models, the liquid film thickness plays an important role and such a fact emphasizes that the accurate measurement of the liquid film thickness is a key point to validate them. On the other hand, several techniques have been successfully applied to measure liquid film thicknesses during condensation and evaporation under macro-scale conditions. However, although this subject has been targeted by several leading laboratories around the world, it seems that there is no conclusive result describing a successful technique capable of measuring dynamic liquid film thickness during evaporation inside micro-scale round channels. This work presents a comprehensive literature review of the methods used to measure liquid film thickness in macro- and micro-scale systems. The methods are described and the main difficulties related to their use in micro-scale systems are identified. Based on this discussion, the most promising methods to measure dynamic liquid film thickness in micro-scale channels are identified.


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Assessment of the Performance of Acoustic and Mass Balance Methods for Leak Detection in Pipelines for Transporting Liquids
Author(s): Martins JC (Martins, Jaqueline Costa), Seleghim P (Seleghim, Paulo, Jr.)
Univ Sao Paulo, Sch Engn Sao Carlos, BR-13566590 Sao Carlos, SP Brazil
Source: JOURNAL OF FLUIDS ENGINEERING-TRANSACTIONS OF THE ASME    Volume: 132    Issue: 1  Article Number: 011401    Published: JAN 2010
Abstract: On-line leak detection is a main concern for the safe operation of pipelines. Acoustic and mass balance are the most important and extensively applied technologies in field problems. The objective of this work is to compare these leak detection methods with respect to a given reference situation, i.e., the same pipeline and monitoring signals acquired at the inlet and outlet ends. Experimental tests were conducted in a 749 m long laboratory pipeline transporting water as the working fluid. The instrumentation included pressure transducers and electromagnetic flowmeters. Leaks were simulated by opening solenoid valves placed at known positions and previously calibrated to produce known average leak flow rates. Results have clearly shown the limitations and advantages of each method. It is also quite clear that acoustics and mass balance technologies are, in fact, complementary. In general, an acoustic leak detection system sends out an alarm more rapidly and locates the leak more precisely, provided that the rupture of the pipeline occurs abruptly enough. On the other hand, a mass balance leak detection method is capable of quantifying the leak flow rate very accurately and of detecting progressive leaks.

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AIChE Journal - Fluid Mechanics and Transport Phenomena

Estimation of mass transfer velocity based on measured turbulence parameters

Johannes G. Janzen 1 *, H. Herlina 2, Gerhard H. Jirka 2, Harry E. Schulz 3, John S. Gulliver 4

1Dept. of Environmental Engineering, Federal University of Rondônia, Jardim dos Migrantes, Ji-Paraná 76900-726, RO, Brazil 2Institute for Hydromechanics, University of Karlsruhe, Karlsruhe 76128, Germany 3Centre of Thermal Engg. and Fluids, Dept. of Hydraulics and Sanitation, São Carlos School of Engineering, University of São Paulo, São Carlos 13560-970, SP, Brazil 4Dept. of Civil Engineering, University of Minnesota, Minneapolis, MN 55455 ABSTRACT The aim of this study is to quantify the mass transfer velocity using turbulence parameters from simultaneous measurements of oxygen concentration fields and velocity fields. The surface divergence model was considered in more detail, using data obtained for the lower range of  (surface divergence). It is shown that the existing models that use the divergence concept furnish good predictions for the transfer velocity also for low values of , in the range of this study. Additionally, traditional conceptual models, such as the film model, the penetration-renewal model, and the large eddy model, were tested using the simultaneous information of concentration and velocity fields. It is shown that the film and the surface divergence models predicted the mass transfer velocity for all the range of the equipment Reynolds number used here. The velocity measurements showed viscosity effects close to the surface, which indicates that the surface was contaminated with some surfactant. Considering the results, this contamination can be considered slight for the mass transfer predictions. © 2009 American Institute of Chemical Engineers AIChE J, 2010 http://www3.interscience.wiley.com/journal/123228386/abstract?CRETRY=1&SRETRY=0